The invention relates generally to an improved lens mounting system for use in field and lens relay systems. Such systems are used in endoscopes and similar optical instruments.
A lens relay system is an optical system consisting of a sequence of lenses that relays the viewed image from lens to lens. Typically each lens relay set in the sequence takes the image from the preceding lens relay set and forms a new image, used as the input to the next lens relay set. The use of a field and lens relay system in an endoscope or other medical device is well known. One well known lens relay system is described in U.S. Pat. No. 3,257,902 and is referred to as the “Hopkins” relay lens system. This system transfers an optical image developed by an objective lens to an adjacent relay lens system or an eyepiece lens and achieves an acceptable level of transfer of a high brightness image with correction of optical aberrations.
One particular challenge in manufacturing such a lens relay system is the mounting of the series of lens such that the lenses are held in the correct position relative to one another and that the lens centerlines remain collinear. One method of mounting a series of lenses is to use a cylindrical mounting tube. Each lens is placed, in order and with spacers, in the mounting tube and slid down to the lens or spacer below it prior to being secured in place. However, this process requires that the outer diameter of each lens to be slightly smaller that the inner diameter of the mounting tube to allow for the lens to be slid down the mounting tube into position. This, in turn, means that the level of precision in mounting each lens is less than ideal as the lens centerlines may not be exactly collinear due to the required space between the lens outer diameter and the mounting tube inner diameter.
There is a need for an improved lens mounting system for use in devices that require a field and lens relay system. In particular, there is a need for a lens mounting system in which lenses can be held in position relative to each other with a high degree of precision such that the lens centerlines remain collinear. In this specification and in the appended claims the term “endoscope” means and should be interpreted to include an endoscope or any other similar optical instrument, whether used for surgery or other applications. In addition the improved lens mounting system is not limited to endoscopes and may be used in any optical application requiring a series of mounted lenses.